Method of controlling the temperature in a fluidized catalyst regeneration process



Jan. 3, 1950 D. CAMPBELL ETAL 2,493,526

METHOD 0F CONTROLLING THE TEMPERATURE IN A FLUIDIZED CATALYST REGENERATION PROCESS Original Filed June 29, 1940 kmw @SEk an; ax 0 w om du Svimko .v exqtfme @N. NN.

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Donald L. Campbell rabam John. 772. G Unvenbqps a (lbbornexq Patented Jan. 3, 1950 METHOD OF CONTROLLING THE TEMPERA- TURE IN A FLUIDIZED CATALYST REGEN- ERATION PROCESS Donald L. Campbell, Short Hills, and John M.

' Graham, Plainfleld, N. J., assignors to Standard Oil Development Com Delaware Daily, a co poration of Original application June 29, 1940, Serial No.

343,080. Divided and this 1944, Serial No. 531,669

2 Claims. (01. 'zsz-m-i 1 This invention relates to a method of controlling temperature and pertains more particularly to controlling reaction temperatures wherein the reactants are passed in indirect heat exchange relation with a fluid medium adapted to add or 5 catalytic material wherein the rate of heat reextract heat from said reactants under closely moval may be more effectively controlled in accontrolled temperature conditions. cordance with changes in the rate of heat gen- While the invention in its broader phases has erated during the operation. a more general application, as will be apparent Other specific objects and advantages of the in a more detailed description hereinafter, it invention will be apparent from the more definds particular application in the regeneration tailed description hereinafter in which reference of powdered catalysts or other-contact materials will be made to the accompanying drawing illuscontaining combustible deposits wherein the trating a side view of an apparatus suitable for powdered material is suspended in a stream of carrying out the present invention. The invenoxidizing gas and the resulting suspension passed tion will be described as applied to the regenthrtiugh atregenerating zone indheat exchange eratignl of plowderedbcatagstist Ieamuployed in mthe rela ion wi h a fluid cooling me ium. crac g of ydrocar on o s, e g unders od' When regenerating many types of catalytic or that in some of its phases it will have a more other contact material it is necessary to regulate general application. the temperature within narrow limits to avoid The amount of heat liberated during regenerapermanently impairing the efliciency of the mation depends to some extent upon the amount terial while at the same time accomplishing the of combustible deposits contained on the cataregeneration within a reasonable time. For exlysts. Consequently as the regeneration proample, in the case ofacid treated and other ceeds and the amount of combustible deposits activated clays employed in the catalytic converremaining on the catalyst progressively diminsion and in the purifying of hydrocarbon oils the ishes the rate of heat generation is correspondactivity of the material is permanently impaired ingly reduced. It is therefore unnecessary and if the regenerating temperature is allowed to exundesirable to remove heat at the same rate ceed the temperature of about 1200 F. for any throughout the full length of the regenerating substanttial tperiod of time. tOn the 0131281 hand 3 zone. the ini ial emperature of he combus ible deg If heat is removed at the same rate throughout posits may be of the order of 800 to 900 and the full length of the regenerating zone the temto efi'ect the rapid regeneration of the catalytic perature of the regenerating stream will be re= material it may be desirable to maintain the duced due to the fact that liberation of heat regenerating zone at a temperature of from 1000 gragsuallgndiminislhes as itigle trl iigeiieratign piloto 1100 F. In such cases, the maximum er- Gee ance W e nven on e missible temperature spread between the i rate of heat removal is decreased as the rate of mum temperature at which the regeneration can heat generation decreases so that the optlmum be accomplished within a reasonable time and temperature is maintained throughout the full the maximum permissible temperature which 40 length of the regenerating zone will avoid deactivating the catalyst is at the In accordance with one of the preferred most between 300 and 400 F and in practical bodiments of the present invention the amount of heat exchange surface per cubic foot of volume operations it IS desirable to maintain the regenis maintained substantially uniform throughout 5523;: i32 g:fi g ggifxz fig ig gggsfi the regenerating zone and the temperature difference causing heat transfer is rogressivel ret to more rapidly regenerate the duced in the direction of the no of the cata lyst. yS This may be accomplished by causing the heat 0119 Of the p nt Objects of the pr s exchange medium to flow concurrently with the invention is to pr v an improved method 0f catalyst and by suitably controlling the rate of regenerating contact material containing comflow a d inl t temperature of the heat transfer bustible deposits. A further object of the invenmedium, For example if it is desired to reduce tion 15 t0 v e n pr d heat exchanger the rate of heat transfer per cubic foot of re- W e e mp ur difference between the generation volume gradually from a certain value cooling medium and products to be cooled may at the inlet to one third of this value at the application April 18,

be more eflectively controlled to prevent temperature "rimaways.

A further object of the present invention is to provide a method of regenerating finely divided outlet it will be possible to attain this end by adjusting the rate of how of heat transfer medium and its inlet temperature so that after the heat of regeneration is added, the outlet temperature difier'ence to cause heat transfer is one third of the temperature difference at the inlet.

As an alternative or supplementary method of regulating the amount of heat removal, the over-all heat transfer coeflicient'may be varied. This may be accomplished for example by withdrawing the cooling medium at spaced points along the regenerating chamber so that the rate of flow of the cooling medium is progressively reduced.- By regulating theamount of heat exchange medium withdrawn at the various points the rate of heat removal along the path of regeneration can be controlled within narrow limits. Also the velocity of the cooling or heat exchange medium may be reduced from the inlet to the outlet of the regenerating zone. "Thismay be accomplished for example by providing transverse baflies to define the path of flow spaced at progressively increasing distances from the inlet to the outlet.

The invention also contemplates a combination of these means for regulating the temperature throughout the regeneration. For example, the reactor may be designed with progressively less heat exchange surface from the inlet to the outlet to take care of normal conditions and the heat exchange medium may be withdrawn at spaced points longitudinally thereof to accommodate unusual fluctuations.

Having set forth the general nature and objects of the invention reference will now be made to the accompanying drawing for a more detailed description thereof. Referring to the drawing the reference character In designates a catalyst chamber from which catalyst to be regenerated is introduced into the regenerating circuit. As illustrated, the top section of the chamber may take the form of a cyclone separator II for removing powdered catalyst from the cracked products from a conversion zone (not shown).

The suspension of cracked vapor products and catalyst may be charged to the separator H I through a line [2. The cracked vapors separated in the cyclone separator II are removed there from through line l3 and may be passed to suit able fractionating and purifying equipment (not shown) for segregating and purifying the desired motor fuel and other products.

Catalyst separated in the cyclone separator ll accumulates in the upper section of the chamber and may be periodically discharged into the ina pressure level substantially higher than is maintained in the cracking circuit. The pressure during regeneration may be for example, of the order of from 3 to or more atmospheres. The catalyst after being subjected to the desired regenerating pressure in the intermediate section I4 of the chamber III is periodically discharged through valved opening IS in the lower partition 20 into bottom section 2| of the chamber III. A

valved by-pass line 22 may be also provided between the intermediate and lower section to equalize pressure during passage of the catalyst from the intermediate to the lower section.

The lower section 2| of the chamber l0 forms a catalyst hopper from which the catalyst is fed at a controlled rate, such as by means of a star feeder 23, into a stream of regenerating gas passing through line 24. The regenerating gas may be air or other oxidizing gas preferably having an oxygen concentration in excess of that required to burn the carbonaceous deposits from the catalyst. Catalyst removed from the cracking zone is normally at a temperature at which oxidation of the carbonaceous deposits is relatively rapid and may be for example from 800 to 950 F. so that combustion starts immediately upon introduction of the catalyst into the regenerating gas.

The suspension of catalyst and regenerating gas then passes directly through line 24 to a regenerating chamber 25. This chamber comprises an outer shell 28 forming an enclosed vessel. The chamber may be suitably insulated to reduce radiation losses. The bottom section of the chamber is provided with a tube sheet 21 which is welded or otherwise suitably secured to the outer shell.

Extending upwardly from the tube'sheet 21 is a bundle of tubes 28 through which the stream of catalyst and regenerating gases pass. The upper end of the tubes terminate in a tube sheet 29 forming the bottom of a floating header 30 which communicates with a tubular conduit 3| extending through a stufiing box 32 in the upper end of the shell. By supporting the tube bundles at one point within the shell the tubes may expand and contract with temperature differences independently of the shell. If desired, guides (not shown) may be provided along the reaction chamber to maintain the tubes and shell in proper alinement.

A plurality of spaced transverse bafiles 33 are provided within the shell and around the tubes to define the flow of cooling medium circulating therein. As shown, the bafiles are preferably spaced at increasing distances from the lower to the upper end so that the velocity of the cooling or heat exchange medium progressively decreases from the inlet to the outlet.

The cooling medium is introduced into the shell at the lower end through port 34 and. cirserve as a heat exchanger for preheating the oil for cracking or for preheating the air introduced into the regenerating stream. A plurality of separate heat exchange sections may be provided for recovering the heat in various ways.

The cooling fluid employed as a heat exchange medium in the regenerating chamber may be of i any suitable high boiling material having the desired melting point such as for example a low melting. metal or alloys or molten salts or salt mixtures.

The cooling medium after passing through they heat exchanger 43 is returned through line 44 and pump 45 to the inlet 34. If desired an inert gas such as steam may be introduced into the top of the reactor through line 41 to provide a gaseous shield above the level of the cooling fluid therein to protect the stuffing box 32. may exhaust through line 53.

There may be added to the apparatus described above a storage'tank (not shown) for the cooling medium interposed between branch lines 39 to 42 inclusive and heat exchanger 43. In case this is done the pump 45 is preferably located between said storage tank and heat exchanger 43.

I The present invention provides a method of controlling reaction temperature wherein rapid surges in temperature are controlled without the necessity of modifying the inlet temperature of the cooling medium. The present invention does not preclude the possibility of aifecting further temperature control by regulating the inlet temperature of the cooling medium. For example a portion of the cooling medium after passing through the regenerator may be bypassed around the heat exchanger 43. Byregulating the relative amount of cooling medium passing through the heat exchanger. 43 and This gas '1. A method of controlling the temperature of exothermic reactions wherein a flowing stream ill '. current to the flow thereof, positively and prothrough by-pass line 46 a relative rapid change in temperature of the cooling medium introduced into the reactor may be obtained.

The suspension of catalyst and regenerating gas after passing through the tubes 28 in the regenerating chamber 25 and the header 30, passes through the conduit 3! and line 49 to a suitable separator such as a cyclone separator 48 for removal of the regenerated catalyst from the regenerating gases. .The regenerating gas may be rejected from the cyclone separator 48 through line 50 and may be expanded through a turbine or passed to any suitable heat recovery apparatus for removal of heat therefrom. Catalyst separated in the cyclone separator 49 may be withdrawn through duct 5| and passed to an injector 52 where it is reintroduced into oil vapors to be cracked. The resulting suspension and oil vapors may then pass to a conversion zone (not shown) wherein the oil vapors are subjected to the desired conversion treatment. The conversion products and catalyst pass through. line It to separator II as previously described.

The outer shell 26 of the regenerating chamber is preferably provided with a valved vent line 53 to release inert gases introduced through line 41 to prevent building up of excessive pressures within the chamber.

This application forms a division of our earlier application Serial No. 343,080, filed June 29, 1940, now abandoned.

Having described the preferred embodiment of the invention it will be understood that it embraces such other variatlons and modifications as come within the spirit and scope thereof. What is desired to be protected by Letters Patent is:

gressively reducing the rate of heat removal from the reactants as they proceed through the reaction'zone by progressively withdrawing cooling medium throughout the length of the reaction zone, the amount of cooling medium so withdrawn being controlled to prevent the temperature of the reaction mixture being reduced during its passage through the reaction zone.

2. A method of regenerating powdered catalytic material containing combustible deposits which comprises the suspending of said catalyst in a gaseous stream containing oxygen in an amount suificient to burn said deposits, passing the resultant catalyst suspension through an elongated unitary regeneration zone maintained at a temperature suificient to burn deposits, passing a cooling medium in indirect heat exchange rela- I tion with the catalyst suspension in the regeneration zone and in a direction concurrent to the flow of said suspension to remove heat liberated during said regeneration, positively and progressively reducing the rate of heat removal from the suspension as it proceeds through the regeneration zone and the rate of burning of the suspension decreases by progressively withdrawing cooling medium throughout the length of the regeneration zone, the amount of cooling medium so withdrawn being controlled to prevent the temperature of the suspension being reduced, its passage through the regeneration zone.

The following references are of record in the file of this patent:

UNITED STATES PA'I'ENTS Number Name Date 1,900,857 Berry et al. Mar. 7, 1933 2,046,816 Fowler et a1. July 7, 1936 2,159,140 Eckell 'et al May 23, 1939 2,163,599 Houdry June 27, 1939 2,227,416 Payne Dec. 31, 1940 2,248,196 Plummer July 8, 1941 2,260,152 Nelly et al. Oct. 21, 1941 4 2,276,307 Houdry Mar. 17, 1942 2,303,717 Arveson Dec. 1, 1942 2,320,273 Gohr et al. May 25, 1943 2,331,433 Simpson et al. Oct. 12, 1943 2,367,281 Johnson Jan. 16, 1945 2,374,660 Belchetz et al. May 1,1945 2,409,596 Simpson et al. Oct. 15, 1946 2,412,917 Simpson et al. Dec. 17, 1946 

2. A METHOD OF REGENERATING POWDERED CATALYTIC MATERIAL CONTAINING COMBUSTIBLE DEPOSITS WHICH COMPRISES THE SUSPENDING OF SAID CATALYST IN A GASEOUS STREAM CONTAINING OXYGEN IN AN AMOUNT SUFFICIENT TO BURN SAID DEPOSITS, PASSING THE RESULTANT CATALYST SUSPENSION THROUGH AN ELONGATED UNITARY REGENERATION ZONE MAINTAINED AT A TEMPERATURE SUFFICIENT TO BURN DEPOSITS, PASSING A COOLING MEDIUM IN INDIRECT HEAT EXCHANGE RELATION WITH THE CATALYST SUSPENSION IN THE REGENERATION ZONE AND IN A DIRECTION CONCURRENT TO THE FLOW OF SAID SUSPENSION TO REMOVE HEAT LIBERATED DURING SAID REGENERATION, POSITIVELY AND PROGRESSIVELY REDUCING THE RATE OF HEAT REMOVAL FROM THE SUSPENSION AS IT PROCEEDS THROUGH THE REGENERATION ZONE AND THE RATE OF BURNING OF THE SUSPENSION DECREASES BY PROGRESSIVELY WITHDRAWING COOLING MEDIUM THROUGHOUT THE LENGTH OF THE REGENERATION ZONE, THE AMOUNT OF COOLING MEDIUM SO WITHDRAWN BEING CONTROLLED TO PREVENT THE TEMPERATURE OF THE SUSPENSION BEING REDUCED, ITS PASSAGE THROUGH THE REGENERATION ZONE. 